Detergent compositions for washing fabrics conventionally contain a detergent active material and a builder material, the latter being added in order, inter alia, to reduce the level of free calcium ions in the wash liquor. While phosphate salts, particularly sodium tripolyphosphate, are often used as builder materials there is an increasing desire to use alternative materials in order to avoid any environmental problems which might arise due to the discharge of phosphate containing waste liquors into rivers and lakes. While a number of alternative builder materials have been suggested, water-soluble carbonates such as sodium carbonate are particularly attractive from the point of view of cost. However, the use of sodium carbonate as a builder material has certain disadvantages, amongst which are the tendency of the precipitated calcium carbonate to become deposited on the fabrics and on surfaces of the washing machine and the sensitivity of the calcium ion/carbonate reaction to poisoning by materials which may well be present, even unintentionally, in the wash liquors resulting in a final free calcium ion concentration which is not as low as is desirable to achieve good detergency.
We have now surprisingly found a class of materials which, if included in detergent compositions containing water-soluble carbonates as builders, are capable of significantly reducing the level of deposition on fabrics and/or washing machine surfaces.
Thus, according to the invention there is provided a detergent composition for washing fabrics which contains:
(i) a detergent active material; PA0 (ii) a water-soluble carbonate material, preferably an alkali metal carbonate, bicarbonate or mixture thereof; and PA0 (iii) an antideposition agent which comprises a calcium containing compound which in a free calcium ion influence test (as herein defined) yields a value of A below 0.5.degree. FH and a value of B above 0.5.degree. FH. PA0 (a) Take 5 cm.sup.3 of the pyrophosphate solution, add 15 cm.sup.3 sulphuric acid (2.5M) and boil for 40 mins. Cool and make up to 25 cm.sup.3 with distilled water. PA0 (b) Take 10 cm.sup.3 of this hydrolysed phosphate solution and add 5 cm.sup.3 distilled water, 3 cm.sup.3 sodium molybdate solution (25 g Na.sub.2 MoO.sub.4.2H.sub.2 O in 1 dm.sup.3 1M sulphuric acid) and 0.5 cm.sup.3 cm sulphate solution (1.5 g NH.sub.2 NH.sub.2 H.sub.2 in 1 dm.sup.3 distilled water). Boil for 15 mins and make up to 25 cm.sup.3. PA0 (c) Measure the absorbance of this solution at 826 nm and compare with standards.
An essential component of the composition according to the invention is a detergent active material. This material may be selected from anionic, nonionic, amphoteric and zwitterionic detergent active compounds and mixtures thereof, particularly such compounds which do not form during use at normal product concentration in hard water excessively water-insoluble calcium salts; this ensures that the detergent active compound is not completely precipitated as its calcium salt instead of calcium carbonate being precipitated. Some degree of precipitation of the detergent active compound or mixture of compounds in the form of the calcium salts may be tolerated, provided that after allowing for the subsequent redissolution of any of the calcium salt during the washing process, the amount of any more permanent precipitate is minor and an effective amount of detergent active compound is left in solution.
Many suitable synthetic detergent active compounds are commercially available and they are fully described in the literature, for example in "Surface Active Agents and Detergents" Volumes 1 and 2, by Schwartz, Perry and Berch.
The preferred detergent active compounds are fully described in GB 1 437 950 (UNILEVER).
The effective amount of the detergent active compound or compounds used in the compositions of the present invention is generally in the range from 5 to 40% by weight, preferably not more than 30% by weight of the composition.
The water-soluble carbonate material used is preferably sodium or potassium carbonate or a mixture thereof, for reasons of cost and efficiency. The carbonate salt is preferably fully neutralised but it may be partially neutralised, for example a sesquicarbonate may be used in partial replacement of the normal carbonate salt; the partial salts tend to be less alkaline and therefore less efficient. The amount of water-soluble carbonate material in the detergent composition can be varied widely, but the amount should be at least 5% by weight, such as from 10% to 40%, preferably 10% to 30% by weight, though an amount of up to 75% could possibly be used if desired in special products The amount of the water-soluble carbonate material is determined on an anhydrous basis, though the salts may be hydrated either before or when incorporated into the detergent composition. It should be mentioned that within the preferred range the higher levels tend to be required under conditions of use at low product concentrations, as is commonly the practice in North America, and the converse applies under conditions of use at higher product concentrations, as tends to occur in Europe. It should be noted that it may also be desirable to limit the carbonate content to a lower level within the range mentioned, so as to decrease the risk of internal damage following any accidental ingestion, for example by children.
The antideposition agent is a calcium containing compound which is characterised by the following free calcium ion influence test.